Prevent Intense New Year Hangover Ethanol is the main active ingredient in alcoholic drinks, but they also contain varying amounts of congeners. Ethanol is the main active ingredient in alcoholic drinks, but they also contain varying amounts of congeners, which are toxic chemicals that include methanol, isopentanol and acetone. Studies show they increase the frequency and intensity of hangovers. Drinks high in congeners include whiskey, cognac and tequila. Bourbon whiskey is exceptionally high in congeners. On the other hand, colorless drinks — like vodka, gin and rum — have low levels of congeners. In fact, vodka contains almost no congeners...